"""
In a string s of lowercase letters, these letters form consecutive groups of the same character.

For example, a string like s = "abbxxxxzyy" has the groups "a", "bb", "xxxx", "z", and "yy".

A group is identified by an interval [start, end], where start and end denote the start and end indices (inclusive) of
the group. In the above example, "xxxx" has the interval [3,6].

A group is considered large if it has 3 or more characters.

Return the intervals of every large group sorted in increasing order by start index.



Example 1:

Input: s = "abbxxxxzzy"
Output: [[3,6]]
Explanation: "xxxx" is the only large group with start index 3 and end index 6.
Example 2:

Input: s = "abc"
Output: []
Explanation: We have groups "a", "b", and "c", none of which are large groups.
Example 3:

Input: s = "abcdddeeeeaabbbcd"
Output: [[3,5],[6,9],[12,14]]
Explanation: The large groups are "ddd", "eeee", and "bbb".
Example 4:

Input: s = "aba"
Output: []


Constraints:

1 <= s.length <= 1000
s contains lower-case English letters only.
"""
from typing import List


class Solution:
    def largeGroupPositions(self, s: str) -> List[List[int]]:
        ret = list()
        n, num = len(s), 1

        for i in range(n):
            if i == n - 1 or s[i] != s[i + 1]:
                if num >= 3:
                    ret.append([i - num + 1, i])
                num = 1
            else:
                num += 1

        return ret


solution = Solution()
print(solution.largeGroupPositions("abbxxxxzzy"))
print(solution.largeGroupPositions("abcdddeeeeaabbbcd"))
print(solution.largeGroupPositions("abc"))
